Our second daughter, [name_f]Britta[/name_f], is due to arrive any day now, and we still haven’t picked a middle name. I’d like to honor my dad by using a girl version of his name- [name_m]Kent[/name_m] (he has 5 granddaughters and it’s probable he won’t ever have a grandson!). Any ideas?!
I might just use [name_m]Kent[/name_m]. [name_m]Kent[/name_m] is also a surname and there is plenty of precedent for surnames as middle names. It sounds good with [name_f]Britta[/name_f] to me. [name_u]Kendall[/name_u] apparently means “valley of the river [name_m]Kent[/name_m]” and [name_f]Kendra[/name_f] would be another option, but I don’t like the “a” ending to [name_f]Britta[/name_f] and [name_f]Kendra[/name_f].
When I saw your title I thought [name_f]Kate[/name_f]. They both have a hard K and a t so the sounds are similar. [name_f]Britta[/name_f] [name_f]Kate[/name_f] could be a less obvious way to honor [name_m]Kent[/name_m].
I love the idea of just [name_f]Britta[/name_f] [name_m]Kent[/name_m], it sounds so cool! Here are some other options. Some of them are a bit of a stretch, but I’m attempting to broaden the horizons. 
[name_f]Britta[/name_f] [name_u]Kendall[/name_u] (using the ken-)
[name_f]Britta[/name_f] [name_u]Kennedy[/name_u]
[name_f]Britta[/name_f] Kentley
[name_f]Britta[/name_f] [name_f]Kenzy[/name_f]
[name_f]Britta[/name_f] [name_f]Mckenzie[/name_f]/[name_f]Mckenna[/name_f]/Mckenzy
[name_f]Britta[/name_f] Maiken/[name_f]Majken[/name_f]
[name_f]Britta[/name_f] [name_f]Millicent[/name_f] (using the -ent)
[name_f]Britta[/name_f] [name_f]Kismet[/name_f] (using the K- & -T)
[name_f]Britta[/name_f] [name_f]Kat[/name_f]/[name_u]Kit[/name_u]
[name_f]Britta[/name_f] [name_f]Keren[/name_f] (using the Ke- & -n-)
[name_f]Britta[/name_f] [name_f]Clementine[/name_f] (using the “ent”)
[name_f]Britta[/name_f] [name_f]Florentia[/name_f]/[name_u]Florentine[/name_u]
[name_f]Britta[/name_f] [name_f]Helisent[/name_f]
[name_f]Britta[/name_f] [name_u]Gentry[/name_u]/[name_f]Jentry[/name_f]
[name_f]Britta[/name_f] [name_m]Laurent[/name_m] (lor-AHN, or lor-OHN if you are from the UK)
[name_f]Britta[/name_f] [name_f]Laurentia[/name_f]/Laurenta
[name_f]Britta[/name_f] [name_f]Magenta[/name_f]
[name_f]Britta[/name_f] [name_f]Valentia[/name_f]/[name_u]Valentine[/name_u]
[name_f]Britta[/name_f] [name_f]Ventura[/name_f]
[name_f]Britta[/name_f] [name_u]Tahoe[/name_u] (means “edge of the lake”, and the name [name_m]Kent[/name_m] means “edge”)
[name_f]Britta[/name_f] Ordel/Ordelle/Ordell (means “valley’s edge”)
Hopefully this helps a bit. Good luck! 
Kenitha is what I thought of immediately.
I actually know a girl with the middle name of [name_m]Kent[/name_m] which is what she prefers to go by. I would probably just use [name_m]Kent[/name_m] but some alernatives I like are:
[name_f]Britta[/name_f] [name_u]Kennedy[/name_u]
[name_f]Britta[/name_f] [name_f]Kenley[/name_f]
[name_f]Britta[/name_f] Kently (Made up but girly)